This invention relates to a method of air jet texturing of continuous filament yarn with an air jet texturing nozzle having a continuous yarn channel at whose one end the yarn is supplied and at whose other end the textured yarn is removed, and compressed air is supplied to the yarn channel in a central section, and in an enlarging acceleration channel the air blast jet is accelerated to a supersonic speed, and loop yarn is produced at a high rate of transport of preferably more than 600 m/min, where the air jet texturing zone is bordered by a feeder roll 1 at the beginning of the air finishing stage and a feeder roll 2 at the end of the air finishing stage.
This invention also relates to a yarn finishing machine with a texturing zone consisting of a feeder roll 1 for supplying the yarn, a texturing nozzle and a feeder roll 2 downstream from the texturing nozzle, where the texturing nozzle has a continuous yarn channel at whose one end the yarn is supplied and at whose other end the textured yarn is removed, and compressed air is supplied to the yarn channel in a central section and an air blast jet at a supersonic speed can be generated in an expanding acceleration channel.
This invention is based on air jet texturing according to International Patent WO97/30200. Finishing of continuous filament yarn must fulfill mainly two functions. First, a textile character is to be imparted to the yarn produced from industrially synthesized filaments, and technical textile properties are to be imparted. Secondly, the yarn is to be finished from the standpoint of specific quality features of the end product which often cannot be achieved with products manufactured from natural fibers. A very important goal with industrially produced filaments and the yarns and textiles produced from them is to optimize the processing operation. Optimizing here means maintaining or increasing certain quality criteria and reducing production costs. It is known that production costs can be reduced in various ways, The most obvious way is to increase throughput speed in a given production facility. Another possibility involves technical process measures that need not necessarily include an increase in throughput speed but instead ensure certain quality criteria even at high yarn throughput speeds.
Especially in the case of continuous filaments, the textile industry is one of the most complex branches of the industry since several independent branches of the industry and commerce are involved from the raw material stage to the finished fabric. None of these branches is completely autonomous, and instead there is a processing chain where any change in process in one stage can influence the following stages or even preceding stages. However, it is still not known whether the final consumer will accept or reject the product after changes with respect to quality properties have occurred due to new process techniques. In some product sectors, especially in filament spinning mills, yarn finishing through yarn finish nozzles is the most important step. The change in structure from smooth yarn to a textured loop yarn is achieved merely through mechanical air forces. Air flow in the supersonic range is generated, as described in the above-mentioned International Patent WO 97/30200. All attempts known so far have shown that the texturing effect hardly changes when using, for example, hot air for the blasting air in the nozzle. The simplest explanation for this is that hot compressed air expands suddenly, cooling at the same time. The heating effect of heated air is mostly lost with this expansion and the corresponding cooling effect.
Unexamined German Patent No. 2,822,538 describes a method of producing PET carpet yarn. This method is stuffer box crimping which is carried out as an integrated process within a spin draw texturing process with transport rates of more than 1800 n/min. In stuffer box crimping, deformation of the yarn is supported chemically in contrast with air jet texturing where air force alone produces the deformation effect.
U.S. Pat. No. 4,040,154 describes another example of stuffer box crimping using superheated steam. Stuffer box crimping here takes place within the cylindrical channel. The yarn leaves the channel without tension. This is in contrast with the actual texturing where the tension produced in the yarn at the outlet from the nozzle provides a measure of the quality of the texturing operation. Texturing was previously often understood in the most general sense and was not taken as a technical concept.
The object of the present invention was to optimize the processing operation in the production of a loop yarn. A portion of the object of this method is then in particular to allow higher yarn transport speeds without any loss of quality..
The method according to this invention is characterized in that the yarn is heated between a first feeder roll and a second feeder roll by an upstream and/or downstream yarn heating device such that both the mechanical air effect and the thermal effect take place between the first feeder roll and the second feeder roll.
FIG. 2 shows with curve T311 a purely schematic diagram of texturing according to the state of the art as stipulated in International Patent WO97/30200. Two main nozzle parameters are emphasized: an opening zone Oe-Z1 and an impinging front diameter DAs starting from a diameter d of the nozzle yarn channel. On the other hand, the diagram shows texturing according to the teaching of International Patent WO97/30200 with an increased output at the upper right of the diagram. This shows very clearly that the values Oe-Z2 and DAE are greater in comparison with those obtained with nozzle T311. Yarn opening begins before the acceleration channel in the area of compressed air supply P, i.e., in the cylindrical section. VO is the pre-opening. Mass Vo is preferably greater than d. The main information from FIG. 1 is the diagramed comparison of the yarn tension Gsp (cN) according to curve T311 at Mach less than  2 and a texturing nozzle according to curve S 315 at Mach greater than  2. The yarn tension is given in cN in the verticals of the diagram. The horizontals show the production speed Pgeschw in m/min. Curve T311 shows the rapid collapse in yarn tension at production speeds of 500 m/min. Above approximately 650 m/min, texturing collapsed. In contrast with that, the curve S 315 shows that the yarn tension is not only much higher but is almost constant in the range of 400 to 700 m/min, and also drops more slowly in the higher production range. The increase in Mach number is one of the most important xe2x80x9csecretsxe2x80x9d for making progress in increasing production output according to International Patent WO97/30200. It was completely surprising that the increase in production output was not exhausted at all with the special design of the acceleration channel. Two central findings make it possible to open another gate to even higher speeds with no loss of quality, namely the additional combination of:
a higher air pressure, and
a thermal treatment before and/or after texturing.
Although in practice, one cannot speak of strictly separate stages in the actual sense, such a representation still comes very close to the actual situation. If a production speed of 1200 m/min is assumed according to the present invention, then 250 m/min of that is due to the increase in pressure to 10-12 bar and an additional 200 m/min is due to the further increase to 12-14 bar (in addition to the effect of heat). According to experiments so far, a further increase in output is readily possible. With an increase in pressure to more than 8 or 9 bar, this merely creates the prerequisite for increasing the Mach number. This is especially effective if the texturing nozzle is designed according to the teaching of International Patent WO97/30200. It may be assumed that even greater increases to 1500 m/min or even more are possible accordingly. According to experiments so far, there is no upper limit to the production rates that can be achieved. Furthermore, another interesting observation is that the thermal effect alone either upstream and/or downstream from the texturing nozzle itself would yield an increase in output with an old nozzle with Mach less than  2. This new invention has shown that there are causal relationships between the increase in pressure, Mach number, yarn transport rate and thermal influence. The stiffness of the individual filaments is reduced with the heat treatment upstream from texturing. Filaments can bend more easily and with less energy when they are warm, which is the main reason for this component. With the heat treatment arranged downstream from texturing, the change in structure that takes place in texturing is more complete. One possible explanation for the surprisingly great effect of the thermal treatment is that with a simultaneous increase in yarn throughput speed, the period of time for possible cooling is also reduced in half Thus, the heat effect is manifested to a greater extent. For especially advantageous embodiments, reference is made to claims 2 through
This invention also concerns a yarn finishing machine and is characterized in that a yarn heating device DK1, DK2 is arranged between two feeder rolls. One heating device DK1 may be located downstream from the texturing nozzle TD and upstream from the second feeder roll LW2, for example, while the other heating device DK2 may be located upstream from the texturing nozzle TD and downstream from the first feeder roll LW1, for example. This invention also relates to the use of a heat treatment upstream and/or downstream from a texturing nozzle that produces an accelerated air flow at supersonic speed, for example more than Mach 2 in the acceleration channel.